Does the pressure in the Klaus system or the exhaust system affect the space velocity inside the reactor?

The ratio of the amount of feed entering the reactor per hour to the reactor’s inventory is called space velocity, abbreviated as SV. Volume space velocity = total feed rate (cubic meters per hour) / catalyst volume (cubic meters). The catalyst volume mentioned here can be understood as the amount of catalyst in the reactor, and it is assumed to be a constant value; therefore, it is the total feed rate that changes! The concept of pressure you are using is not accurate; the concept of pressure difference is more appropriate. The greater the pressure difference, the higher the flow rate, and the more material passes through the reactor per unit time, which means a higher space velocity! If it’s pressure, then when the pressure at the front is high and the pressure at the back is also high, the pressure difference doesn’t change much, so it has little impact on the air velocity! The same goes for the other way around!

I understand what you mean. You’re saying that the greater the pressure difference between the inlet and outlet of the reactor, the higher the flow rate of gas inside the reactor, and the more catalyst surface area is passed through per unit time; in other words, the space velocity increases. I get that. But I’m wondering whether only the exhaust gas pressure, or the pressure in the Claus system, has an impact on the space velocity

Regardless of the location, the differential pressure must be taken into consideration; otherwise, it’s an incomplete problem!

By adjusting the opening of the system valves to artificially increase the system pressure, the residence time of the process gas within the system can be extended, which is beneficial for the progress of the reaction. However, in reality, the flow rate of the process gas entering and leaving the system per unit time remains unchanged; based on the definition of space velocity, the space velocity of the reactor also stays constant.

This post was last edited by ylb913 on 2017-8-26 at 22:19 to organize the thoughts, as they were a bit messy. What can be confirmed is: 1. The concept of space velocity is: flow rate (cubic meters per hour divided by the volume of the bed in cubic meters). 2. The lower the space velocity, the longer the reaction time. 3. The higher the pressure, the lower the actual volumetric flow rate and the lower the space velocity. The premise is that the quantity remains unchanged (molar amount, or standard flow rate). Is it stated in some sources that the air velocity increases when the pressure rises? I don’t know what this means. I understand that the air velocity should be the volumetric flow rate under operating conditions, not the standard volume, and I’m too lazy to do the calculations today.

There seems to be a possibility of conceptual confusion here. First, the volume space velocity refers to the space velocity under normal conditions; space velocity = normal-condition flow rate of the feed gas (Nm3/h) / catalyst volume (m3) ； Then, the residence time is calculated based on the ratio of the catalyst volume to the actual flow rate; Residence time = Catalyst volume (m3) / Actual flow rate of the feed gas (m3/h) ； In industry, there is a tendency to increase the reaction pressure because raising the pressure speeds up the reaction rate and increases the throughput per unit volume (or mass) of catalyst. With the same volume (or mass) of catalyst, a larger amount of feed gas can pass through at high pressure, thereby increasing the space velocity of the reactor. The increase in pressure simultaneously compresses the volume of the feed gas, increasing the residence time of the components on the catalyst surface. I’m not sure if it was clear enough.